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Nygrunnen GroupNYGRUNNEN GROUP (M-100) STATUS OF UNIT: Formal FIRST USE OF NAME: Worsley et al. 1988 CURRENT DEFINITION: Worsley et al. 1988 SYNONYM(S) AND REFERENCE(S): None ORIGIN OF NAME: Nygrunnen: A fishing bank NW of Sørøya, northern Norway TYPE AREA: Block 7121/12, Hammerfest Basin. Blocks 7121/5 and 7120/12 show a thinner development typical of central and southeastern basin areas STRUCTURAL SETTING: Tromsø and Hammerfest basins, Bjarmeland Platform (Southern Barents Sea Shelf) DEPOSITIONAL AGE: Late Cenomanian - Maastrichtian OVERLYING UNIT(S): Sotbakken Group (Palaeogene) UNDERLYING UNIT(S): Adventdalen Group SUPERIOR UNIT: None OTHER USE OF NAME: None THICKNESS: 50-250 m in the Hammerfest Basin, 1200 m in the Tromsø Basin MAIN LITHOLOGIES: Sandstone, claystone, limestone DESCRIPTION: The Nygrunnen Group shows a distinctly twofold development. The Tromsø Basin was the depositional centre throughout most of the period. Areas farther east were either only transgressed at times of maximum sea level and/or display only condensed sections. Greenish grey to grey claystones with thin limestone intervals in the Tromsø Basin (Kveite Formation) pass eastwards and southwards into a more calcareous, or sandy, condensed succession (Kviting Formation). Open marine, deep shelf environments in the west passed into shallower, starved regimes (uplifted at times) in the east. The unit has no correlatives in Svalbard, where the entire Upper Cretaceous is represented by a major hiatus. KVEITE FORMATION (M-101) OCCURRENCE: Offshore unit, known from the Hammerfest Basin (Fig. 1-02) STATUS OF UNIT: Formal FIRST USE OF NAME: Worsley et al. 1988 CURRENT DEFINITION: Worsley et al. 1988 SYNONYM(S) AND REFERENCE(S): None ORIGIN OF NAME: Kveite: Norwegian for the fish species 'halibut' (Hippoglossus hippoglossus) TYPE SECTION: Stratotype: Exploration well 7119/12-1. Hypostratotype: Exploration well 7119/7-1 DEPOSITIONAL AGE: Late Cenomanian - Early Maastrichtian DATING METHOD: Palynology REFERENCE(S) FOR AGE: No published data available; dated by Worsley et al. (1988) on the basis of proprietary oil company data. OVERLYING UNIT(S): Torsk Formation (Palaeogene) UNDERLYING UNIT(S): Kolmule Formation SUPERIOR UNIT: Nygrunnen Group OTHER USE OF NAME: None THICKNESS: 249 m (stratotype), 1200 m (hypostratotype) MAIN LITHOLOGIES: Shale, mudstone, limestone LOWER BOUNDARY DEFINITION: The formation is characterised by a lower gamma response and higher interval transit time than the underlying unit. A basal sand in the type well gives a marked break in both these logs. The boundary in these wells is also marked by a sudden increase in bulk density values above a generally decreasing trend, but the formation as a whole shows a highly variable and irregular density response. DESCRIPTION: The Kveite Formation consists of greenishgrey to grey shales and mudstones with thin interbeds of limestone and siltstone. A tuffaceous and/or glauconitic component is present in several wells. The formation appears to be characteristically developed in the Tromsø Basin and across the Ringvassøya - Loppa Fault Complex into the Hammerfest Basin, thinning eastwards and passing into the sandstones and carbonates of the Kviting Formation. The deposits indicate deep, open shelf environments with normal water circulation. Back to top KVITING FORMATION (M-102) OCCURRENCE: Offshore unit, known from the Hammerfest Basin (Fig. 1-02) STATUS OF UNIT: Formal FIRST USE OF NAME: Worsley et al. 1988 CURRENT DEFINITION: Worsley et al. 1988 SYNONYM(S) AND REFERENCE(S): None ORIGIN OF NAME: Kviting: Norwegian for the fish species 'whiting' (Merlangius merlangus) TYPE SECTION: Stratotype: Exploration well 7120/12-1. Hypostratotype: Exploration well 7121/5-1 DEPOSITIONAL AGE: Campanian DATING METHOD: Palynology REFERENCE(S) FOR AGE: No published data available; dated by Worsley et al. (1988) on the basis of proprietary oil company data. OVERLYING UNIT(S): Torsk Formation (Palaeogene) UNDERLYING UNIT(S): Kolmule Formation SUPERIOR UNIT: Nygrunnen Group OTHER USE OF NAME: None THICKNESS: 17 m (stratotype), 31 m (hypostratotype) MAIN LITHOLOGIES: Sandstone, mudstone LOWER BOUNDARY DEFINITION: The base is defined in the type well by log breaks showing a sharp decrease in gamma response and interval transit time, and increasing density. DESCRIPTION: The Kviting Formation consists of calcareous sandstones with interbedded sandy and glauconitic mudstones. Limestones in the reference well are interbedded with, and grade up into sandy mudstones. The formation is apparently restricted to the central and eastern parts of the Hammerfest Basin. Deep to shallow shelf environments are indicated. Back to top |